Carbon brush



(No Model.)

B. THOMSON.

CARBON BRUSH.

No.- 539,454. Patented May 21, 1895.

V\/I ESSES- |[\]\/E 011 WWW ELL mm Q, V91). MIA

UNITED STATES PATENT OFFICE.

ELlllU Tl'lOidSON, OF SWAMPSOOTT, MASSACHUSETTS, ASSIGNOR, BY MESNE ASSIGNMENTS, TO THE GENERAL ELECTRIC COMPANY, OF SOHENECTADY,

NEW YORK.

CARBON BRUSH.

SEEGZFIFATION forming part of Letters Patent No. 539,454, dated May 21, 1895.

Application tiled February 6, 1895. Serial No. 537,458. (No model.)

To all whom it; may concern.-

Be it known that I, ELIHU Trronson, a citi- Zen of the United States, residing at Swampscott, in the county of Essex, State of Massachusetts, have invented certain new and useful Improvements in Carbon Brushes for Electric Apparatus, of which the following is a specification.

The present invention relates to commuta- IO tor brushes; and has for its object to produce an improved commutator brush as herein set forth.

The particular object of my invention is to improve the conductivity of the brush while {5 preserving its elasticity and to provide a large number of contact points for the reception or delivery of current from the brush, the different parts of'the brush adapting themselves by their elasticity or flexibility to surfaces which are not altogether true.

Another object of my invention is to reduce to a minimum the pressure which has to be applied to a brush, particularly when composed mainly of carbon, in order to secure Sill'llClOillZ contact with the commutator, it being well known that where solid masses of carbon are applied to commutators a very slight contact only is secured unless the surfaces in contact are perfectly true and run- 0 ning in practically true directions.

Figure 1 shows a brush constructed in accordance with this invention. Fig. 2 is an edge view of the same. Fig. 3 is a view of a modification, and Fig. 4 is an edge view of the same.

Referring to Fig. 1, the commutator brush is made as follows: A number of thin strips or filaments of carbon, 1, (which may be of carbonized cellulose in any of its forms, and

4,0 which may or may not be subjected to hydrocarbon treatmeut for solidifying or filling the pores, as is commonly done with incandescent lamp filaments) are taken and lightly coated on their exterior with copper, 2, or with other 5 metal, nickel being preferred in some cases, on account of its elasticity being superior to that of copper. This metal sheath around the filament stiffens the filament, strengthens it, and affords a superior resistance to flexure. The numerous strips, which maybe Very fine according to the design for which the brush ,is to be used, are taken and laid together parallel and soldered at one end, as at 3, Figs. 1 and 2, while at the other end, where the filaments are to be applied to tho commutator 5 or metal surface, they are left free and not united, as in the ordinary wire brush. This surface is generally beveled, and the brush is applied at an angle, or at a partial tangentto the commutator. This beveling is indi- 6o cated at 4c in the figures. The brush is held as a metal wire brush would be held, and is preferably backed by a plate 5 of thin copper or other metal. The under side or surface may also be provided with a similar plate to 63 make the brush resist the pressure of the holder more readily, or the plate 5 may be carried all around and form a thin metallic casing for the brush, the flexible ends of which project a little toward the commutator. On account of the elasticity and flexibility of the free ends of the coated filaments of carbon, there is presented to the commutator a brush which furnishes contacts at large number of points, each point being capable of carrying a fraction of the current. The elasticity and flexibility of the end of the brush enable it to adapt itself readily to slight irregularities of surface, so that but a light pressure need be employed in using it to col- 8o lect or deliver current. In this respect it is decidedly different from carbon brushes as hitherto made, and resembles more nearly metal brushes, but has in addition to the characteristics of a metal brush the distinct quality of a much higher general specific resistance, and at the same time, each filament presents to the surface of the commutator a carbon wearing facet, the metal surrounding each filament being quickly removed or burned away go during use, so that a portion of the brush is, in a measure and so far as the wearing of the commutator goes, like that of a carbon brush requiring little or no lubrication, and giving a polished surface to the commutator, while 9 5 the other features of the brush are like those of a metal wire brush, the advantages of both brushes being combined.

lVhile in Figs. 1 and 2 it is assumed that filamentary strips or long shreds of carbon rco have been coated with metal and brought together, it is by no means essential to my invention that this be done, as I may employ a woven fabric which has been carbonized and then plated lightly before assembling. It may then be rolled up in a mass, or be assembled in layers. This is shown in Figs. 3 and 4, where Fig. 3 is a view of such a brush made from a woven carbonized fabric 6 with a portion of the outer metallic sheath or coating 7, which it is preferable to employ, shown broken away. The fabric itself is made of any closely woven fabric which gives a hard carbonaceous residue on carbonization; or it may be specially woven of threads of cellulose made as in the ordinary process of manufacturing filaments for incandescent lamps, such threads'of cellulose while new and flexible being woven together as-wire is woven to form wire gauze. After this is done the mass is carbonized in a closed cruicible or muffie,

out of contact with air, or surrounded by carbon dust, is then removed and immersed in a plating bath and given a thin coating of metal, as of copper or nickel. The layers are then collected together to the required thickness, &c., for the brush, and preferably soldered at the end 8 farthest from the wearing end, so as to hold the layers in relative position, after which they may be slipped into a thin metallic outer case which supports the brush and gives it greater rigidity, said case terminating at or near the point of contact or wearing surface which bears upon the commutator.

What I claim as new, and desire to secure by Letters Patent of the United States, is

1. A commutator brush made of filamentary carbon coated with metal, and mounted I in a casing for strengthening it.

2. A commutatorbrush composed of filamentary carbon connected together in layers or strips to the required thickness and size assembled together to the required thickness,

and are united at one end and inclosed with a strengthening casing.

5. A flexible commutator brush made of carbonized strips of fibers, the'fibers inclosed or incased in conducting metal, whereby their conductivity is increased, and their elasticity and strength also increased.

6. Acommutator brush formed of filaments of carbon coated with metal, secured together at one end and loose at the other.

7. A commutator brush formed of filaments of carbon coated with metal, secured together at one end and free at the other end, and provided with a strengthening casing.

8. A commutator brush formed of filaments of carbon coated with metal and woven together, and arranged in layers secured together at one end and free at the other end.

9. A commutator brush formed of layers of woven filaments of carbon coated with metal, and arranged in layers secured together at one end and free at the other end, with a strengthening casing.

In witness whereof I have hereunto set my hand this 2d day of February, 1895. 4

ELinU THOMSON.

Witnesses:

JOHN W. GIBBONEY, HENRY O. WEsTENDARP; 

